The present invention is related generally to the art of confidential viewing of display images. More particularly, the present invention is directed to confidential viewing of a fundamental display image on a liquid crystal display (LCD) by utilizing auto-inversion masking to mask or neutralize the fundamental image so as to render it indecipherable to the naked eye, whereby image decoding is available only to the intended viewer.
With the increasing use of video displays for a variety of systems, such as those used in desktop computers, laptop computers, televisions, and personal video entertainment systems, there exists an increasing need and desire to provide confidential viewing of these displays by only those who the displayed content is intended for, thus eliminating the possibility of unauthorized viewing.
Various devices have been introduced over the years to prevent unauthorized viewing of video displays. The simplest devices generally include a form of “anti-glare” privacy screen and/or hoods and shields. These devices are commonly found on desktop computer displays which are intended to restrict viewing to only those who are more or less directly in front of the display. While these are somewhat effective, they cannot prevent viewing by someone peering over ones shoulder, and thus are far from secure.
Other devices have been developed which seek to obscure the view of a fundamental image from an unintended viewer by introducing a “masking image.” In some devices, the masking image is introduced as an obscuring secondary light source. In others, the masking image is spatially multiplexed in some manner with the fundamental image; and in still others, the masking image is alternately displayed with the fundamental image at the vertical synch rate of the display device. These later systems, however, are largely dependent on the speed or refresh rate of the display and, although can be used with an LCD, are generally better suited for use with faster conventional CRT displays. With typical LCD displays, the required display refresh rate to provide flicker free performance is simply too high.
The LCD, however, due to its flat screen, thin profile, high resolution, and low power consumption, has become the display of choice for use with most portable laptop computers, where incidentally, the need for confidential viewing is likely to be the greatest. In this regard, some devices more specific to the LCD have been introduced which seek to provide confidential viewing by removing the top polarizing layer of the LCD screen. This renders the display “invisible” except to those wearing polarized glasses. In one such device, as discussed in U.S. Pat. No. 6,650,306, modulation of the LCD's liquid crystal display cell is introduced as a means of enhancing security. The viewing means is then configured with a synchronous liquid crystal rotator to decode the intended image for viewing. Devices of this type, however, are generally incapable of being readily switched between “confidential” and “standard” viewing modes, and typically require specialized eyewear to be worn at all times.
Given the desire and need for a simple and effective means of display security, and the limitations of the prior art, it is apparent that a better means is needed for providing confidential viewing of a standard LCD, which can be readily switched between standard and confidential viewing modes and used in all applications of full color/full motion graphics and images.
It is believed that my LCD-based confidential viewing apparatus utilizing auto-inversion masking techniques described hereafter accomplishes this end while greatly enhancing the viewing security of video displays today.